/b\  5+ 


HAWAII  AGRICULTURAL  EXPERIMENT  STATION 

HONOLULU,  HAWAII 

Under  the  supervision  of  the 
UNITED  STATES  DEPARTMENT  OF  AGRICULTURE 


BULLETIN  No.  54 


EDIBLE  CANNA  IN  HAWAII 


BY 

H.  L.  CHUNG,  Specialist  in  Tropical  Agronomy 

and 

J.  C.  RIPPERTON,  Chemist 


Issued  July  1924 


s.  7^: 


WASHINGTON 
GOVERNMENT  PRINTING   OFFICE 

1924 


HAWAII  AGRICULTURAL  EXPERIMENT  STATION,  HONOLULU 

{Under  the  supervision  of  the  Office  of  Experiment  Stations,  United  States  Department  of  Agriculture] 

E.  W.  Allen,  Chief,  Office  of  Experiment  Stations. 

Walter  H.  Evans,  Chief,  Division  of  Insular  Stations,  Office  of  Experiment  Sta- 
tions. 


STATION   STAFF 

J.  M.  Westgate,  Agronomist  in  Charge. 

W.  T.  Pope,  Horticulturist. 

H.  L.  Chung,  Specialist  in  Tropical  Agronomy. 

J.  C.  Ripperton,  Chemist. 

R.  A.  Goff,  In  Charge  of  Glenwood  Substation  and  Extension  Agent  for  the  Island 

of  Hawaii. 
Mabel  Greene,  Boys'  and  Girls'  Club  Leader. 


HAWAII  AGRICULTURAL  EXPERIMENT  STATION 
HONOLULU,  HAWAII 

Under  the  supervision  of  the 
UNITED  STATES  DEPARTMENT  OF  AGRICULTURE 


BULLETIN  No.  54 


Washington.  D.  C  July,  1924 


EDIBLE  CANNA  IN  HAWAII 

By  H.  L.  Chung,  Specialist  in  Tropical  Agronomy,  and  J.  C.  Ripperton,  Chemist 


CONTENTS 


Page 

I  nt  roduct  ion 1 

Botanical  description 2 

Climatic  and  soil  requirements 3 

Methods  of  culture 3 

Yield 6 

Keeping  qualities 6 


Page. 

Insects  and  diseases 7 

Composition 7 

Feeding  value 12 

Edible  canna  starch 13 

Uses 15 

Summary 16 


INTRODUCTION 

Edible  canna  (Canna  edulis),  known  also  as  the  Queensland  arrow- 
root, Australian  arrowroot,  adeira  (Peru),  and "tous-les-mois*'  (West 
Indies),  is  indigenous  to  South  America,  where  it  is  found  growing  in 
Brazil,  Peru,  and  Trinidad.1  In  many  tropical  countries  the  tub- 
erous roots  are  cooked  as  a  vegetable,  but  in  South  America  and  in 
several  of  the  colonies  of  Australia  the  plant  is  cultivated  chiefly  for 
the  sake  of  its  starch.2 

The  exact  length  of  time  edible  canna  has  been  growing  in  Hawaii  is 
not  known,  but  it  is  thought  that  the  plant  was  introduced  into  the 
islands  about  the  year  1898.3  The  first  planting  at  the  Agricultural 
Experiment  Station  was  made  December  8,  1915,  from  a  small 
quantity  of  tubers  received  from  Judge  J.  A.  Matthewman,  Kailua, 
Hawaii.  A  large  number  of  the  plants  were  afterwards  distributed 
throughout  the  Territory  for  the  purpose  of  utilizing  the  tubers  for 
food  in  case  of  necessity  during  the  food  shortage  incident  to  the 
World  War.  The  tubers  are  not  popular  as  a  vegetable  in  Hawaii 
because  of  the  length  of  time  required  to  cook  them.  The  tops, 
however,  furnish  a  large  amount  of  excellent  forage  for  cattle  and 
poultry,  and  the  plant  now  occupies  a  well-established  place  among 
stock  feeds. 

n-h  has  been  manufactured  from  edible  canna  for  more  than 
50  yean  in  Queensland,  Australia,  but  the  industry  was  not 
successfully  launched  in  Hawaii  until   L922,  although  1  he  experiment 

i  Textbook  of  tropical  agriculture,  p.  2>>:5.    U.  A.  Aiford  Nicholls. 

1  Tropical  agriculture:  A  treatise  on  the  culture,  propagation,  commerce,  Bad  consumption  of  the  prin- 
cipal products  of  the  vegetable  kingdom,  p.  344,  345.     I'.  L.  EUmmonds. 
i.  Rpt.  1917,  p.  51. 

96956— 24f 1 


2  BULLETIN  .  54,    HAWAII   EXPERIMENT   STATION 

station  had  repeatedly  made  experimental  starch  extractions  to 
demonstrate  the  possibilities  of  the  crop.  Much  interest  is  at  present 
being  manifested  in  the  growing  of  edible  canna  for  commercial 
starch  production,  and  thousands  of  .acres  of  the  uplands,  which 
are  not  suited  to  pineapple  and  sugar  cane  growing,  have  shown  con- 
siderable adaptability  to  the  crop. 

BOTANICAL  DESCRIPTION 

Edible  canna  is  a  member  of  the  family  Cannacese,  and  is  closely 
related  to  the  common  flowering  varieties  which  are  grown  as  orna- 
mentals in  many  parts  of  the  world  (fig.  1) .     It  is  perennial  in  tropical 


Fig.  1.— A  field  of  edible  canna  ready  for  harvesting. 

countries,  and  is  propagated  either  by  means  of  young  shoots  which 
are  detached  from  the  parent  stool,  or  by  underground  fleshy  corms, 
commonly  called  tubers  or  rootstocks,  which  are  very  rich  in  starch. 
The  tubers  vary  from  cylindrical  to  tapering  and  spherical  to  oval, 
ranging  from  2  to  3J  inches  in  diameter  and  from  4  to  6  inches  in 
length  (fig.  2).  The  stems  are  usually  stout,  and  are  tinged  with 
dark  lavender  which  is  rather  pronounced  at  the  base  of  the  very 
young  shoots.  They  grow  in  clumps  averaging  12  stems  each, 
attain  a  height  of  4  to  8  feet,  depending  upon  climatic  and  soil  con- 
ditions, and  blossom  in  4  to  6  months  in  Hawaii.  The  flowers  are 
bright  red  with  narrow  petals.  The  seed  pods  are  usually  large  when 
normally  developed,  but  in  most  cases  produce  no  viable  seed. 


EDIBLE    CANNA   IN    HAWAII  3 

CLIMATIC  AND  SOIL  REQUIREMENTS 

The  luxuriant  growth  made  by  edible  canna  in  various  locations  of 
widely  differing  altitude  in  Hawaii  would  seem  to  indicate  that  the 
crop  is  not  exacting  in  its  climatic  requirements.  It  thrives  from  sea 
level  to  an  elevation  of  2,700  feet  near  Waimea,  Island  of  Hawaii. 
In  short  growing  periods,  however,  the  crop  produces  its  maximum 
yield  at  an  elevation  of  less  than  1,500  feet  and  when  the  days  and 
nights  are  relatively  warm,  the  rainfall  is  adequate,  and  protection 
is  afforded  against  strong  winds. 

As  is  true  of  other  root  crops,  edible  canna  makes  its  best  develop- 
ment when  it  is  grown  in  a  loose,  loamy  soil  containing  an  abundance 
of  humus.     When  the  crop  is  grown  in  a  clay  soil,  the  yield  is  materi- 


Fig.  2.— A  typical  edible  canna  corm. 

ally  reduced  and  the  size  of  the  individual  tubers  considerably  di- 
minished. Clayey  soil  renders  difficult  the  work  of  harvesting  and 
usually  causes  the  plant  to  make  a  poor  stand.  Edible  canna  will 
withstand  an  excessive  amount  of  moisture  in  the  form  of  rainfall  and 
irrigation,  but  it  will  not  grow  in  soil  that  is  not  well-drained. 

METHODS  OF  CULTURE 

SELECTION  OF  PLANTING  STOCK 

Only  tubers  which  have  attained  normal  size  and  development 
and  bear  one  or  more  healthy,  unbruised  buds  should  be  selected 
for  planting  (fig.  3).  As  a  precautionary  measure  against  rot- 
producing  organisms,  the  station  dips  all  tubers  at  the  time  of  dig- 
ging in  a  10  per  cent  solution  of  copper  sulphate. 


4  BULLETIN   54,    HAWAII   EXPERIMENT   STATION 

PREPARATION  OF  THE  LAND 

Edible  canna  should  be  planted  on  land  that  has  been  thoroughly 

E  lowed  and  cleared  of  weeds  and  debris.  Loose,  loamy  soil  should 
e  plowed  to  a  depth  of  8  inches  and  then  worked  down  with  a  disk 
harrow.  Clayey  soil  should  be  given  two  plowings  a  week  or  more 
apart.  Just  before  the  second  plowing  is  given,  manure,  or  any 
form  of  vegetable  matter,  should  be  scattered  over  the  soil.  The 
physical  condition  of  clayey  soil  will  be  greatly  benefited  by  an 
application  of  manure  or  of  slaked  lime  (at  the  rate  of  2  tons  per 
acre).  Deep  plowing,  especially  on  clayey  soils,  is  essential  to  the 
successful  production  of  edible  canna  since  it  gives  the  roots  a  larger 
feeding  area  than  they  would  otherwise  have. 


Fig.  3. — Stages  of  maturity  in  the  growth  of  the  edible  canna  tuber.  (A)  Old.  An  undesirable 
type  of  corm  for  planting.  (B)  Mature.  A  desirable  seed  corra  for  propagation.  Adventitious 
buds  insure  quick  growth.     (C)  Immature. 


PLANTING 

In  the  Hawaiian  Islands,  where  the  temperature  is  fairly  uniform 
throughout  the  year,  edible  canna  may  be  planted  at  any  season 
except  during  a  period  of  drought,  and  even  then  if  irrigation  is 
available.  Maturing  sufficiently  for  harvesting  in  eight  months, 
the  crop  should  occupy  the  ground  during  the  eight  most  favorable 
months  for- growth,  unless,  of  course,  the  immediately  preceding  or 
following  crop  is  entitled  to  primary  consideration. 

In  a  loose,  loamy  type  of  soil,  the  tubers  should  be  planted  5 
inches  deep  at  distances  of  3  feet  in  rows  that  are  3  feet  apart.  A 
spacing  of  3  by  3  feet  will  permit  of  planting  4,840  hills  per  acre, 
and  render  cross-cultivation  possible  while  the  plants  are  young.  In 
a  heavy  type  of  soil,  the  planting  distance  should  be  increased  to 
4  feet  each  way,  and  the  tubers  planted  not  more  than  3  inches 
deep.     The  increased  distance  will  permit  of  cultivation  until  the 


EDIBLE    CANNA   IN    HAWAII  5 

crop  has  grown  to  considerable  size.  The  tubers  should  be  dropped 
bv  hand  into  furrows  that  are  made  by  an  animal-drawn  plow. 
At  the  station,  a  plank  drag  has  been  effectively  used  to  cover  the 
tubers  to  the  proper  depth. 

CULTIVATION 

Edible  canna  readily  responds  to  good  cultivation.  As  soon  as 
the  plants  are  6  inches  high,  the  ground  should  be  cultivated  with 
a  tooth  harrow  which  is  properly  adjusted  to  cover  the  width  of 
the  rows.  Heavier  cultivators  can  be  used  to  advantage  with  the 
increased  growth  of  the  crop.  Cross-cultivation  thoroughly  stirs 
the  soil  and  enables  the  tubers  to  make  good  growth.  Hard,  com- 
pact soil  causes  them  to  become  stunted.  At  the  station,  the  last 
cultivation  is  usually  given  about  4  months  after  planting.  From 
this  time  on,  cultivation  is  almost  impossible  because  of  the  spread- 
ing growth  of  the  clumps  of  stalks.  Weed  growth,  however,  is  then 
effectually  kept  down  and  smothered  out  by  the  luxuriant  foliage 
which  shades  the  ground. 

FERTILIZERS 

Little  is  known  regarding  the  fertilizer  requirements  of  edible 
canna.  In  a  preliminary  experiment  conducted  by  the  station,4 
fertilizers  were  found  to  have  a  marked  effect  upon  yield.  Of  the 
fertilizers  applied,  ammonium  sulphate,  superphosphate,  and  potas- 
sium sulphate  (250  pounds  each)  gave  the  highest  yield.  From 
10  to  15  tons  of  well-rotted  manure  should  be  applied  per  acre  im- 
mediately after  the  first  plowing,  being  thoroughly  worked  into  the 
soil  by  disking.  This  will  not  only  furnish  plant  food  for  the  grow- 
ing crop,  but  will  also  greatly  improve  the  texture  of  the  generally 
compact  and  heavy  soils  of  Hawaii. 

ROTATION 

Edible  canna  is  well  adapted  to  either  long  or  short  rotation 
periods.  It  is  recommended,  however,  that  the  crop  be  treated  as 
an  8-months'  crop,  although  harvesting  may  be  delayed  for  several 
months  longer  without  seriously  affecting  either  yield  or  quality. 
The  crops  recommended  for  rotation  are  (1)  corn,  followed  by 
edible  canna,  peanuts,  and  cowpeas  (plowed  under) ;  (2)  alfalfa 
(2  or  3  years),  followed  by  corn,  cassava,  pigeon  peas  (plowed  under), 
and  edible  canna;  and  (3)  beans,  followed  by  corn,  edible  canna, 
peanuts,  cowpeas,  and  sweet  potatoes.  It  is  important  that  the 
land  be  freed  from  nut  grass,  which  is  not  only  extremely  aggressive 
but  also  very  hard  to  combat  in  a  stand  of  this  plant. 

IRRIGATION 

The  plant  resists  drought  reasonably  well,  and  will  stand  a  great 
deal  of  moisture  when  the  area  on  which  it  is  grown  is  well-drained. 
Whenever  the  rainfall  is  insufficient  to  meet  the  full  water  require- 
ments of  the  crop  irrigation  should  be  practiced,  the  ground  being 
thoroughly  soaked  twice  a  month.  One  heavy  irrigation  is  worth 
ral  light  irrigations. 

*  Hawaii  Sta.  Rpt.  1918,  p.  48. 


6  BULLETIN   54,    HAWAII   EXPERIMENT   STATION 

HARVESTING 

Edible  canna  has  no  definite  period  for  maturing.  In  Queensland , 
its  growth  is  checked  in  late  fall  by  the  frosts,  and  the  plant  begins 
to  die  back  at  any  time  during  the  next  few  months.  In  the  Hawaiian 
Islands,  where  frosts  do  not  occur,  the  plant  continues  to  grow 
indefinitely,  and  it  is  difficult  to  determine  the  time  tubers  should 
be  harvested  to  obtain  the  maximum  yield.  If  grown  for  stock 
feed,  the  crop  need  not  be  removed  from  the  ground  until  it  is  wanted 
for  use.  No  labor-saving  devices  for  harvesting  edible  canna  have 
been  invented  or  adapted  to  Hawaiian  conditions.  The  stalks 
are  cut  down  with  a  cane  knife  or  other  sharp  instrument,  and  the 
entire  stool  is  dug  up  with  a  spading  fork  or  mattock.  In  some 
instances  a  plow  is  successfully  used  to  loosen  up  the  soil  adjoining 
the  hills  or  stools.  As  soon  as  the  tubers  are  dug  the  roots  and 
adhering  earth  should  be  removed.  If  the  crop  is  wanted  for  stock 
feed,  the  tubers  can  be  held  for  several  weeks  without  injury. 
Tubers  which  are  to  be  used  for  starch  production  should  be  taken 
to  the  mill  immediately  after  digging  in  order  that  exposure  may 
have  no  deteriorating  effect  on  the  quality  of  the  manufactured 
product.5 

YIELD 

Yields  vary  with  the  rainfall  and  soil  of  the  different  regions  in 
which  the  crop  is  grown.  At  the  Glenwood  substation,  7  tons  of 
tubers  were  obtained  with  a  9-months'  growing  season.6  At  the 
Castner  substation,  28  tons  of  tubers  were  obtained  in  12  months 
from  a  soil  to  which  manure  was  applied.  A  year  later,  yields 
ranging  from  18  to  23  tons  were  obtained  in  the  same  locality.7 
At  Waimea,  Hawaii,  it  is  reported  that  40  to  50  pounds  of  tubers 
have  been  obtained  in  single  hills  of  edible  canna.  The  first  trial 
planting  at  the  station  (Honolulu)  yielded  at  the  rate  of  43  tons  of 
tubers  per  acre  in  24-J  months  after  planting.8  Subsequent  tests 
gave  results  varying  from  10  tons  of  tubers  within  4  months  after 
planting  to  34  tons  within  12  months  after  planting,  with  an  average 
yield  ranging  from  18  to  20  tons  per  acre  for  8-month  periods. 

KEEPING  QUALITIES 

One  of  the  important  features  of  the  plant  is  the  excellent  keeping 
qualities  of  its  tubers.  Original  seed  tubers  have  been  known  to 
remain  in  excellent  condition  when  left  unharvested  in  the  ground 
for  a  year  or  more.  The  tubers  may  be  harvested  and  kept  from 
decay  for  seed  purposes  for  at  least  three  months  provided  that 
they  are  cleansed  of  adhering  soil  and  are  thoroughly  dried  before 
being  put  in  storage.  The  storage  place  should  be  kept  cool  and 
dark.  The  tubers  may  be  piled  in  heaps  not  over  2  feet  high. 
Higher  stacking  prevents  proper  circulation  of  the  air  and  may 
result  in  the  tubers  decaying.  The  tubers  may  be  stored  in  the 
field  for  a  short  time  if  the  weather  is  dry.  Results  of  experiments 
conducted  at  the  station  would  seem  to  indicate  that  tubers  can  be 

»  Queensland  Agr.  Jour.,  v.  X,  Pt.  I,  p.  36,  Tropical  industries:  Arrowroot,  its  cultivation  and  manu 
facture. 

•  Hawaii  Sta.  Rpt.  1919,  p.  71. 

•  Hawaii  Sta.  Rpt.  1919,  p.  47. 

•  Hawaii  Sta.  Rpt.  1917,  p.  51. 


EDIBLE    CANNA   IN    HAWAII  7 

kept  in  the  field  in  good  condition  for  one  month  when  they  are 
stacked  in  heaps  not  over  2  feet  high  and  are  covered  with  canna 
tops.  In  two  months'  time,  the  tubers  that  are  nearest  the  ground 
will  have  started  to  germinate. 

INSECTS  AND  DISEASES 

This  plant  is  remarkably  free  from  both  insect  pests  and  plant 
diseases.  Grasshoppers  and  Japanese  beetles  are  occasionally 
found  feeding  on  the  foliage  when  more  desirable  host  plants  are 
not  available,  but  their  damage  is  negligible.  In  Waimea,  Hawaii, 
cutworms  are  the  most  destructive  pests  of  canna.  Their  injuries 
in  certain  seasons  are  confined  to  the  tender  young  shoots  which 
are  either  devoured  or  completely  cut  off  at  the  base  of  the  growing 
plant.  The  following  poison  baits  are  recommended  as  control 
measures: 

Paris-green-bran  mash. — Thoroughly  mix  25  pounds  of  bran  with  one-half  pound 
of  Paris  green.  Add  to  the  mixture  6  finely  chopped  lemons  or  1  quart  of  cheap 
molasses.  Stir  well,  and  add  sufficient  water  to  moisten.  Do  not  make  the 
mixture  so  thin  that  it  can  not  be  easily  and  economically  distributed. 

Small  patches  should  be  treated  with  1  ounce  of  Paris  green  to  3  pounds  of 
bran,  and  one-half  cup  of  molasses.  Four  to  six  times  as  much  by  weight  of 
arsenate  of  lead  should  be  used  as  in  case  of  the  Paris  green,  and  only  half  as 
much  white  arsenic. 

Poisoned  succulent  foliage.— Fresh  cut  alfalfa  or  other  succulent  foliage  which 
is  attractive  to  the  insects  may  be  sprayed  with  Paris  green  or  arsenate  of  lead 
mixtures,  and  the  poisoned  leaves  and  stems  scattered  in  the  infested  fields. 

Criddle  mixture. — Large  areas  may  be  treated  with  fresh  horse  dung,  salt, 
and  Paris  green,  in  the  proportions  of  60,  2,  and  1  pounds,  respectively,  per  acre. 
This  mixture  is  equally  as  effective  and  not  as  expensive  as  bran.  The  Paris 
green  should  be  stirred  into  enough  water  to  form  a  thin  paste  and  then 
thoroughly  mixed  with  the  manure.  Five  pounds  of  arsenate  of  lead,  or  one- 
half  pound  of  white  arsenic,  may  be  used  instead  of  the  Paris  green. 

Rats,  which  occasionally  gnaw  young  tubers,  can  be  brought 
under  control  by  the  use  of  traps  and  poisoned  bait. 

A  field  of  canna  will  sometimes  present  a  burned  appearance  in 
the  dry  season,  due  to  the  drying  effect  of  hot  winds. 

COMPOSITION 

In  two  analyses  made  at  the  station,  edible  canna  was  found  to 
vary  in  water  content  from  65.86  to  81.58  per  cent,  and  in  nitrogen- 
free  extract  from  15.57  to  31.34  per  cent.9  The  other  constituents 
showed  corresponding  differences  when  expressed  as  percentages  of 
dry  material. 

In  making  a  study  of  the  value  of  the  crop  as  a  feed  and  as  a 
commercial  source  of  starch,  it  is  obviously  necessary  that  determina- 
tion be  made  of  its  average  chemical  composition  and  of  the  varia- 
tion- which  take  place.  This  is  particularly  important  in  case  of 
the  edible  canna,  which  has  no  regular  period  for  maturing  and 
continues  to  grow  indefinitely.  On  this  account  there  has  been  a 
great  difference  of  opinion  as  to  the  best  age  at  which  to  harvest  the 
tubers  for  maximum  starch  production.  In  some  cases  the  crop  is 
harvested  after  a  growing  period  of  6  months,  while  in  others  it  is 
allowed  to  grow  for  18  months  or  more.  Crops  which  differ  so  greatly 
in  age  would  probably  have  appreciable  differences  in  composition. 

•Hawaii  Sta.  Press  Bui.  53,  p.  9.  ♦ 


BULLETIN    54,    HAWAII   EXPERIMENT   STATION 


VARIATION  IN  COMPOSITION  OF  THE  TUBERS 

In  order  to  determine  what  progressive  changes  take  place  in  the 
composition  of  the  tubers,  samples  for  analysis  were  harvested  each 
month  from  a  field  at  the  station,  beginning  with  the  sixth  month 
after  planting  and  continuing  through  the  twelfth  month.  Only 
one  sample  was  analyzed  during  each  of  the  first  three  months.  As 
the  work  progressed  it  became  apparent  that,  due  to  the  short  life 
cycle  of  the  canna,  the  variations  in  the  composition  of  tubers  within 
a  single  hill  were  greater  at  any  time  than  they  were  between  compos- 
ite samples  that  were  harvested  a  month  apart.  In  order  to  deter- 
mine the  monthly  variations  of  the  entire  hill  and  the  individual 
differences  taking  place  within  the  hill,*the  tubers  harvested  during 
the  last  three  months  were  divided  into  three  groups  having  the 
following  characteristics : 

(1)  Old  tubers  (cylindrical  to  oval  in  shape).  The  tops  of  the 
tubers  were  dead.  The  gradual  tapering  of  the  tuber,  as  compared 
with  tubers  in  group  2,  shows  that  in  the  late  stage  of  growth  starch 
is  stored  in  the  lower  two  or  three  inches  of  the  stalk,  which  then, 
for  starch  manufacture,  becomes  an  integral  part  of  the  tuber. 

(2)  Mature  tubers  (oval  to  round  in  shape).  The  plants  had 
reached  the  bloom  stage.  The  tubers  were  mature  and  had  attained 
their  maximum  diameter. 

(3)  Immature  tubers  (round  in  shape).  The  tops  of  the  plants 
were  either  just  above  ground  or  had  not  as  yet  emerged.  The  tubers 
were  of  course  smaller  than  in  case  of  either  of  the  preceding  groups. 

Roots,  dead  scales,  and  adhering  soil  were  all  removed  from  the 
tubers  as  soon  as  they  were  dug.  After  being  weighed,  shredded, 
and  dried,  the  tubers  were  analyzed  by  the  methods  recommended 
by  the  Association  of  Official  Agricultural  Chemists.10 

Chemical  analyses  of  the  tubers,  which  were  harvested  monthly, 
are  given  in  the  following  table : 

Effect  of  stage  of  maturity  of  harvesting  on  the  percentage  composition  of  edible  canna 

tubers  a 


0 

Water 

Protein 

Fat 

Carbohydrates 

Age 

Nitrogen- 
free 
extract 

Crude 
fiber 

Ash 

Fresh  material 
Six  months    ..... 

Per  cent 
80.58 
77.53 
76.09 

Per  cent 

0.94 

.71 

.56 

Per  cent 

0.07 

.08 

.09 

Per  cent 
16.72 
19.95 
21.62 

Per  cent 

0.40 

.39 

.40 

Per  cent 
1.29 

Seven  months.  . 

1.34 

Eight  months... 

1.24 

Nine  months: 

Mature6 

70.10 
77.26 

.77 
.94 

.10 
.08 

27.10 
19.74 

.67 
.51 

1.26 

Immature . 

1.47 

Average .     ..     .. 

73.68 

.86 

.09           23.42 

.59 

1.36 

Ten  months: 

Old 

72.49 
68.78 
76.18 

.79 
1.01 
1.25 

.12 
.12 
.  11 

24.41 

28.25 
20.44 

.79 
.51 
.48 

1.40 

Mature 

1.33 

Immature  .. 

1.54 

Average . 

72.48 

1.02 

.  12           24.  37 

.59 

1.42 

«  The  results  are  given  on  the  oven-dry  weight  as  well  as  on  the  fresh  material  because  the  former  brings 
out  more  clearly  the  variations  in  the  composition  of  the  different  groups  of  tubers. 

t>  Sample  includes  both  old  and  mature  tubers. 

10  Methods  of  analysis  orthe  Association  of  Official  Agricultural  Chemists,  sec.  VII,  p.  71-99.  Revised  to 
Nov.  1,  1919,  Washington.  D.  C,  1920. 


EDIBLE    CANNA   IN    HAWAII 


Effect  of  stage  of  maturity  of  harvesting  on  the  percentage  composition  of  edible  canna 

tubers — Continued 


Water 

Protein 

Fat 

Carbohydrates 

Age 

Nitrogen- 
free 
extract 

Crude 
fiber 

Ash 

Fresh  material— Continued 

Eleven  months: 

Old 

Per  cent 
67 

66.77 
70.25 

Per  cent 
0.93 
1.07 
1.00 

Per  cent 

0.12 

6.12 

.13 

Per  cent 
29.65 
30.06 
26.49 

Per  cent 

0.88 

0.55 

.61 

•  Per  cent 
1.42 

Mature 

1.43 

Immature 

1.52 

A  verage. . . 

68.01 

1.00 

.12 

28.73 

.68 

1.46 

Twelve  months: 

Old 

71.92 
75.41 
81.68 

.87 
1.01 
1.2 

.10 
.09 
.07 

25.18 

21.5 

15.09 

.73 
.51 

.57 

1.20 

Mature. 

1.48 

Immature 

1.39 

Average.. 

76.33 

1.03 

.09 

20.59 

.60 

1.36 

Oven-dried  material 
Six  months. 

4.83 
3.14 
2.33 

.36 
.34 
.37 

86.08 

88.8 

90.43 

2.08 
1.75 
1.69 

6.65 

Seven  months . 

5.97 

Eight  months 

5. 18 

Nine  months: 

Mature  fc 

2.58 
4.13 

.35 
.34 

90.6 
86.8 

2.25 
2.27 

4.22 

Immature..  . 

6.46 

Average 

3.36 

.34 

88.7 

2.26 

5.34 

Ten  months: 

Old 

2.87 
3.21 
5.23 

.43 

.39 
.44 

88.76 
90.51 
85.86 

2.86 
1.64 
2.02 

5.08 

4.25 

Immature 

6  45 

Average 

3.77 

.42 

88.38 

2.17 

5  26 

Eleven  months: 

Old 

2.8 
3.21 
3.34 

.37 
.35 
.44 

89.85 
90.51 
89.06 

2.67 
1.64 
2.04 

4  31 

Mature 

4.29 

Immature 

5.12 

Average . .. 

3.12 

.39 

89.8 

2.12 

4.57 

Twelve  months: 

Old 

3.09 
4.15 
6.61 

.35 
.35 
.38 

89.71 
87.42 
82.33 

2.58 
2.07 
3.1 

4  27 

Mature .. 

6.01 

Immature 

7.58 

A  verage 

4.62 

.36 

86.49 

2.58 

5.95 

*>  Sample  includes  both  old  and  mature  tubers. 

The  transition  from  immaturity  to  maturity  and  thence  to  post- 
maturity is  a  very  gradual  one,  and  it  is  impossible  to  select  from 
monthly  harvests  tubers  that  have  reached  the  same  stage  of  maturity, 
because  of  the  short  life  cycle  of  the  plant.  Obviously,  some  of  the 
variations  given  in  the  preceding  table  are  due  to  faulty  sampling. 

In  general,  however,  the  above  data  show  that,  with  respect  to 
variations  among  the  three  groups  of  tubers,  the  moisture  content  is 
always  the  greatest  in  the  immature  tubers.  Apparently  it  decreases 
until  the  tubers  reach  the  mature  stage,  after  which  it  remains  fairly 
constant.  In  several  instances  there  are  slight  increases  in  the 
moisture  content  of  the  old  tubers  over  the  mature  ones. 

Kxpressed  as  percentages  of  dry  weight,  the  protein  and  ash  show 
a  considerable  decrease  in  the  transition  of  tin  tubers  from  immaturity 
to  maturity,  while  the  crude  fiber  of  the  mature  tubers  is  in  each 
instance   less    than    in   case   of    the   old    tubers.     The   nitrogen-free 


10 


BULLETIN   54,    HAWAII   EXPERIMENT   STATION 


extract  is  always  lowest  during  immaturity,  while  in  two  out  of  three 
instances  it  is  higher  during  maturity  than  in  the  older  stages. 

A  comparison  of  the  average  composition  by  months  shows  no 
consistent  variations  other  than  a  gradual  decrease  in  the  moisture 
content  up  to  the  twelfth  month.  This  is  to  be  expected  because  the 
ages  of  the  mature  and  immature  tubers  of  the  several  months  are 
about  the  same  regardless  of  the  month  of  harvest.  Since  the  tubers 
vary  little  in  composition  after  they  reach  the  mature  stage,  the  hill 
as  a  whole  should  show  little  variation  in  composition  from  month 
to  month. 

The  twelfth-month  samples  show  an  abrupt  change  in  composition 
as  compared  with  samples  of  the  preceding  months.  The  water 
content  made  an  average  increase  of  more  than  8  per  cent,  whereas  it 
showed  a  continuous  decrease  in  the  preceding  months.  Coupled 
with  the  high  protein  and  ash  content  of  the  immature  groups,  this 
change  is  indicative  of  new  and  quick  growth.  That  such  was  the 
case  is  shown  by  the  fact  that  at  11  months  from  planting,  21  hills 
of  canna  contained  397  immature  tubers  and  a  total  yield  of  183 
pounds,  while  at  12  months  from  planting,  a  like  number  of  hills 
contained  671  immature  tubers  and  a  total  yield  of  303.5  pounds. 
Unfortunately,  this  field  was  plowed  before  a  further  study  could  be 
made.  It  is  highly  probable,  however,  that  with  the  return  of 
normal  weather  conditions  the  average  composition  of  the  hill 
eventually  would  have  become  the  same  as  it  had  been  in  the  period 
preceding  the  twelfth  month. 

In  brief,  it  may  be  concluded  that  after  an  individual  tuber  has 
reached  maturity,  which  requires  from  30  to  90  days,  it  varies  little 
in  composition  at  least  for  a  year,  except  for  an  appreciable  increase  in. 
fiber  content;  and  provided  that  weather  conditions  remain  constant, 
the  composition  of  the  hill  as  a  whole  changes  little.  Consequently, 
the  crop  will  have  practically  the  same  composition  regardless  of 
the  age  at  which  it  is  harvested.  The  best  age  at  which  to  harvest 
may  therefore  be  decided  largely  by  the  yields  obtained.  The 
analyses  as  given  in  the  preceding  table  show  the  following  to  be  the 
average  composition  of  edible  canna  tubers : 

Chemical  composition  of  edible  canna 


Constituent 

Fresh 
material 

Oven- 
dried 
material 

Constituent 

Fresh 
material 

Oven- 
dried 
material 

Water 

Per  cent 

72.62 

.98 

.11 

Per  cent 

Per  cent 

24.28 

.61 

1.40 

Per  cent 
88.  6S 

Protein 

3.58 
.40 

2.2a 

Fat  (ether  extract) ... 

Ash 

5. 1L 

VARIATION  IN  COMPOSITION  OF  THE  TOPS 

Since  canna  tops  may  attain  maximum  growth  in  as  short  a  time 
as  30  days  under  proper  climatic  conditions,  it  would  seem  as  though 
rapid  changes  in  composition  must  take  place.  To  permit  of  a. 
study  of  such  changes,  the  tops  of  a  hill  12  months  old  were  divided 
into  three  stages  of  growth:  (1)  Old  stage,  in  which  the  blooms  were 
dead  and  the  lower  leaves  were  beginning  to  wither;  (2)  bloom  stage; 
and  (3)  immature  stage  averaging  2  feet  in  height.  The  following 
table  shows  the  effect  of  the  stage  of  maturity  on  the  composition 
of  canna  tops. 


EDIBLE    CANNA   IN    HAWAII  11 

Effect  of  stage  of  maturity  on  the  percentage  composition  of  canna  tops 


Water 

Protein 

Fat 

Carbohydrates 

Ash 

Stage  of  maturity 

Nitrogen- 
free 
extract 

Fiber 

Nutritive 
ratio 

Fresh  material 
Old  tops 

Per  cent 
88.67 

Per  cent 
1.07 
1.13 
1.12 

Per  cent 

0.33 

.23 

.14 

Per  cent 
5.83 
5.32 
3.20 

Per  cent 
2.77 
2.46 
1.70 

Per  cent 
1.33 
1.47 
1.37 

1  : 6. 14 

Mature  tops 

89.39 

1  :  5. 17 

92.47 

1  :  3. 14 

Average 

90.18 

1.11 

.23 

4.78 

2.31 

1.39 

1  :  4. 81 

Ocen-dried  material 
Old  tops 

.       

9.47 
10.68 
14.94 

2.95 
2.14 
1.91 

51.40 
50.15 
42.44 

24.45 
23.15 
22.50 

11.73 
13.88 
18.21 

Mature  tops... 

Immature  tops 

Average 

11.70 

2.33 

48.00 

23.37 

14.60 

The  above  table  shows  that  all  the  samples  analyzed  contained 
a  high  percentage  of  moisture  which  decreased  with  increasing  matur- 
ity; and,  likewise,  that  the  percentage  of  fat,  nitrogen-free  extract, 
and  fiber  increased,  while  the  ash  and  protein  decreased,  with  in- 
creasing maturity.  The  nutritive  ratio  of  the  old  tops  was  100  per 
cent  wider  than  in  case  of  the  immature  group. 

COMPOSITION  OF  EDIBLE  CANNA  GROWN  IN  WAIMEA 

Waimea,  Hawaii,  gives  promise  of  becoming  an  important  canna- 
producing  region.  In  this  district,  where  the  system  of  fanning 
resembles  the  grain  and  stock  farms  of  the  Mississippi  Valley,  the 
repeated  failure  of  most  of  the  staple  crops  has  forced  homesteaders 
to  cultivate  some  crop  wiiich  can  be  depended  upon  as  a  source  of 
feed.  Edible  canna  has  shown  itself  to  be  especially  wrell  adapted 
to  the  high  altitude  and  high  winds  of  the  region,  and  could  be  utilized 
both  as  a  stock  feed  and  as  a  commercial  source  of  starch.  It  grows 
luxuriantly  notwithstanding  such  adverse  conditions  as  high  winds, 
low  temperature,  and  drought.  With  the  return  of  favorable  condi- 
tions new  buds  develop  and  growth  proceeds  without  the  stunting 
effect  so  manifest  in  most  other  crops.  The  soil  at  Waimea  is  ideal 
for  canna  culture,  being  of  a  porous  nature,  in  striking  contrast 
with  most  of  the  easily  compacted  soils  of  the  islands. 

Three  samples  of  canna  were  obtained  from  Waimea  for  analysis, 
one  consisting  of  very  old  tubers,  and  the  other  twTo  corresponding 
to  the  mature  and  immature  types  described  on  page  8.  The  old 
tubers  had  been  in  the  ground  ior  over  two  years  and  gave  no  evi- 
dence of  decay  except  for  a  slight  darkening  of  the  tissue.  The 
surfaces  bore  deep  cracks,  which,  however,  had  healed  without 
decay.  The  tops  of  the  new  growth  had  been  repeatedly  cut  for 
feed,  leaving  the  tubers  partly  exposed.  The  following  table  shows 
the  effect  of  stage  of  maturity  on  the  composition  of  canna  tubers 
which  were  grown  in  Waimea. 


12 


BULLETIN   54,    HAWAII   EXPERIMENT   STATION 


Effect  of  stage  of  maturity  on  the  percentage  corn-position  of  edible  canna  grown  at 

Waimea 


Water 

Protein 

Fat 

Carbohydrates 

Stage  of  maturity 

Nitrogen- 
free 
extract 

Crude 
fiber 

Ash 

Fresh  material 
Old      .     . 

Per  cent 
75.85 
74.68 
82.63 

Per  cent 
0.66 
1.41 
1.17 

L08~ 

Per  cent 

0.10 

.11 

.07 

Per  cent 
21.59 
22.19 
14.43 

Per  cent 

0.69 

.53 

.52 

Per  cent 
1. 11 

1.08 
1.18 

Immature 

Average 1 

77.72 

.09 

19.40 

.58 

1.13 

Oven-dried  material 
Old 

2.72 

5.56 
6.76 

.41 
.44 
.40 

89.43 
87.66 
83.05 

2.86 
2.08 
2.98 

4.58 

Mature.     ..                    ...  .      

4.26 

Immature 

6.81 

5.01 

.42 

86.71  I 

5.22 

In  general,  the  above  table  shows  that  canna  from  Waimea  has 
the  same  composition  as  that  grown  at  the  central  station.  It  also 
shows  similar  variations  in  composition  among  the  three  types  of 
tubers.  As  a  result  of  remaining  in  the  soil  for  two  years,  the  old 
tubers  showed  a  smaller  proportion  of  protein,  but  a  slightly  larger 
proportion  of  water,  than  did  the  mature  tubers. 


FEEDING  VALUE 

At  the  present  time  both  tubers  and  tops  are  used  largely  as  stock 
feed.  The  tubers  may  be  fed  raw,  but  are  usually  shredded  and 
cooked  first.  Goff  "  reported  that  the  tops  were  fed  by  hog  raisers 
on  Hawaii  with  no  other  preparation  than  cutting  them  into  6-inch 
lengths.  When  fed  with  soured  rice  bran,  the  tops  caused  the  animals 
to  gain  steadily  in  weight. 

Although  the  station  has  conducted  no  extensive  feeding  tests 
with  canna  tops  for  horses  and  mules,  its  four  work  mules  have  been 
observed  to  eat  them  readily  and  sometimes  to  leave  their  grain 
for  the  tops. 

The  following  table  compares  the  composition  and  feeding  value 
of  edible  canna  and  other  forage  and  starch  crops: 

Comparison  of  the  percentage  composition  and  feeding  value  of  edible  canna  and 
other  starch  and  forage  crops 


Crop 


Part  of 
plant 


Water 


Protein 


Fat 


Carbohydrates 


Nitro- 
gen-free 
extract 


Crude 

fiber 


Ash 


Nutritive 
ratio 


Edible  canna. 
Taroo 


Sweet  potato  «. 

Cassava  a 

Potato  6.. 

Napier  grass  c . 
Para  grass  <*... 


Per  cent 
/Tubers... 

\Tops 

/Tubers... 

\Tops 

/Tubers... 
\Tops 

Tubers... 

Tubers... 


Per  cent 
72.62 
90.18 
60.55 
84.56 
68.89 
87.67 
64.17 
78.30 
61.81 
74.60 


Per 


cent 
0.98 
1.11 
1.10 
1.86 
2.12 
2.93 
.77 
2.20 
2.92 
2.28 


Per  cent 
0.11 
.23 
.13 
.49 
1.26 
.36 
1.59 
.10 
.29 
.29 


Per  cent 
24.28 

4.78 
36.91 
10.29 
27.02 

6.08 
31.42 
18.00 
17.29 
10.92 


Per  cent  , 
0.61 
2.31  ; 

.58  i 
1.42 

.81  ! 
1.69 
1.19  ' 

.40 
14.77  ; 
9.10 


Per  cent 
1.40 
1.39 

.73 
1.38 

.90 
1.27  | 

.86 
1.00 
2.92 
2.81  I 


1 :  25.0 
1:4.8 

1:33.8 
1:6.1 

1:14.1 
1:2.4 

1 :  45.4 
1:8.3 
1:6.1 
1:5.1 


o  Hawaii  Sta.  Press  Bui.  No.  53,  pp.  8.  9,  and  10:  Composition  and  digestibility  of  feeding  stuffs  grown 
in  Hawaii.  .  . 

b  U.  S.  Dept.  Agr. ,  Office  of  Experiment  Station  Bui.  No. 28  (revised) ,  p.  68.  The  chemical  composition 
of  American  food  materials. 

c  Philippine  Islands  Jour.  Prog.  Agr.,  v.  IV,  no.  9,  p.  27:  Napier  grass. 

<*  Hawaii  Sta.  Bui.  No.  13,  p.  8:  The  composition  of  some  Hawaiian  feeding  stuffs. 

ii  Hawaii  Sta.  Rpt.  1919,  p.  71. 


Bui.   54.    Hawaii   Agr.    Expt.  Station. 


Plate  I 


i 

r\  y 

N— '      -\ 

"^  w 

) 

# 

r  "* 

Fig.   I. — Edible  Canna  Starch.     Magnified  220  Diameters. 


Fig.  2.     Potato  Starch.     Magnified  220  Diameters. 


Bui.  54,   Hawaii  Agr.   Expt.  Station. 


Plate  II. 


Fig.   I. — Corn  Starch.     Magnified  220  Diameters. 


. 

- 

/fus^j 

i 

' 

Fig.  2. — Cassava  Starch.     Magnified  220  Diameters. 


EDIBLE    CANNA   IN    HAWAII  13 

The  table  on  page  12  shows  that  edible  canna  tubers  have  about 
the  same  feeding  value  as  other  tuberous  crops  possessing  a  nutritive 
ratio  that  is  narrower  than  that  of  cassava  or  taro,  and  wider  than 
that  of  potatoes  or  sweet  potatoes.  As  a  forage  crop,  the  tops 
compare  favorably  with  other  crops.  They  are  succulent  and  have 
a  comparatively  narrow  nutritive  ratio.  Compared  with  the  grasses, 
they  are  lower  in  crude  fiber  and  higher  in  protein,  calculated  on  a 
dry-weight  basis.     Low  and  high  protein  are  both  advantageous. 

EDIBLE  CANNA  STARCH 

Chemically,  all  starches  are  alike,  being  the  condensation  product 
of  dextrose  and  having  the  general  formula  (C6H1005)n.  In  this 
formula,  however,  "n  varies  between  wide  limits,  ranging  from 
about  30  to  200  or  more.  The  value  of  "n"  and  the  space  arrange- 
ment within  the  starch  granule  are  subject  to  great  variation  and 
give  rise  to  striking  physical  differences.  When  determining  the 
character  of  a  starch,  it  is  necessary,  therefore,  to  study  only  its 
physical  properties. 

IDENTIFICATION 

Morphologically,  edible  canna  starch  is  characterized  by  its 
exceptionally  large  granules.  (PI.  I,  fig.  1.)  Its  identifying  char- 
acteristics are  as  follows:  Shape,  irregular,  ovoid;  hilum,  eccentric 
and  annular;  rings,  plainly  visible;  length,  0.04  to  0.13  millimeters; 
with  polarizer,  well  defined  cross  at  hilum  is  visible  both  with  and 
without  selenite  plates. 

Edible  canna  starch  and  potato  starch  are  somewhat  alike  in 
appearance,  the  chief  difference  being  in  the  hilum,  which  is  annular 
and  not  so  prominent  in  canna  starch,  and  occurs  as  a  spot  in  potato 
starch.  In  the  latter  the  small  grains  are  almost  round,  with  the 
hilum  central.  In  the  potato  starch  both  large  and  small  granules 
occur  in  about  equal  proportion  (PL  I,  fig.  2),  whereas,  in  the  canna 
starch  the  large  ones  greatly  predominate.  For  purposes  of  com- 
parison the  starches  of  corn  and  cassava  are  shown  in  Plate  II, 
figures  1  and  2. 

VISCOSITY 

When  a  starch  is  heated  in  water  to  a  temperature  that  is  suf- 
ficiently high  to  break  the  granules  it  becomes  colloidal  in  nature. 
The  viscosity  of  this  so-called  " soluble  starch"  is  to  some  extent  a 
measure  of  its  value  for  certain  uses,  as  for  example,  in  the  textile 
industry. 

The  viscosity  of  colloidal  starch  can  be  made  to  vary  between 
wide  limits.  The  time  and  method  of  cooking,  the  temperature, 
and  the  concentration  greatly  affect  the  total  viscosity.  If  the 
solution  is  vigorously  shaken  while  it  is  hot  the  viscosity  can  be 
reduced  to  as  little  as  one-half  of  its  value  without  such  agitation. 
The  viscosity  increases  with  decreasing  temperature  and  the  starch 
hydrogel  changes  to  a  definite  hydrogel  if  the  solution  is  sufficiently 
concentrated.  Different  samples  of  starch  from  the  same  source 
often  show  pronounced  differences  in  viscosity 


14 


BULLETIN   54,    HAWAII   EXPEBIMENT  STATION 


Apparently,  therefore,  certain  arbitrary  conditions  must  be  con- 
formed to  when  the  viscosity  of  a  starch  is  measured.  The  viscosity 
thus  observed  holds  true  only  for  these  conditions.  The  method  of 
procedure  adopted  for  this  study  was  as  follows:  Varying  amounts 
of  starch  were  Weighed  into  100  cubic  centimeter  flasks  graduated 
at  80°  C,  and  shaken  with  10  .cubic  centimeters  of  cold  water. 
Boiling  water  was  then  added  with  vigorous  shaking  and  the  flask 
made  up  to  the  mark  at  80°  C.  with  hot  water.  After  thorough 
mixing  they  were  placed  in  boiling  water  for  one  hour  without 
agitation.  They  were  then  quickly  cooled  to  80°  C.  with  as  little 
agitation  as  possible  and  the  viscosity  determined  at  this  tempera- 
ture by  means  of  a  Saybolt  standard  viscosimeter.  Results  can  be 
duplicated  with  fair  accuracy  at  80°  C.  but  will  vary  widely,  prob- 
ably due  to  the  tendency  of  the  colloid  to  form  a  plastic  gel,  if  the 
solution  is  cooled  to  room  temperature. 


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-Comparison  of  the  viscosities  of  various  solutions  of  edible  canna  starch,  potato  starch,  corn 
starch,  and  cassava  starch. 


The  Saybolt  universal  viscosimeter  is  essentially  a  cylindrical  tube 
having  a  diameter  of  3  centimeters,  a  height  of  10  centimeters,  and  a 
capacity  of  70  cubic  centimeters.  The  bottom  of  the  tube  is  con- 
stricted to  an  opening  1.77  millimeters  in  diameter.  The  tube  is  sur- 
rounded by  a  water  or  oil  bath  so  that  any  desired  temperature  can 
be  maintained.  The  viscosity  is  determined  by  filling  the  tube  with 
the  solution  to  be  tested,  and  noting  the  time  necessary  to  fill  a  flask 
of  exactly  60  cubic  centimeters  capacity  through  the  opening  in  the 
bottom  of  the  tube.  This  type  of  viscosimeter  is  probably  not  so 
well  adapted  for  the  measurement  of  the  viscosity  of  starches  as  is 
the  torsion  viscosimeter,  which  would  have  less  destructive  effect  on 
the  easily  affected  structure  of  the  starch  solution. 

A  comparison  of  the  viscosities  of  various  solutions  of  edible  canna 
starch,  potato  starch,  corn  starch,  and  cassava  starch  are  given  in 
the  following  table,  and  also  graphically  in  Figure  4. 


EDIBLE    CANNA   IN    HAWAII 

Comparison  of  viscosity  of  edible  carina  starch  and  other  starches 


15 


Starch 

Viscosity  (Saybolt)  at  80°  C  « 

solution 

Edible 
canna 

Potato 

Corn 

Cassava 

Per  cent 

Min.  Sec. 

Min.  Sec. 

Min.  Sec. 

Min.  Sec. 

0.5 

...      31 

...      33 

...      30      ...       28 

1.0 

...      33 

...       41 

...      32     ...      32 

1.5 

...      38 

1      29 

...      36      ...       35 

2.0           1       10 

3      24 

...      42  !   ...       48 

2.5           2      19 

9     ... 

...      54         1       .. 

3. 0           7      15 

21     ... 

1      35         1      46 

3. 5         20      15 

6      45         3      13 

4.0       

13      40         4      57 

4.5       



24      32         7      27 

•  Twenty-eight  seconds  are  required  to  run 
viscosimeter. 


i  cubic  centimeters  of  distilled  water  at  80°  C.  through  the 


From  the  above  table  it  is  apparent  that  potato  starch  possesses  a 
greater  viscosity  than  do  either  of  the  other  two  starches.  Canna 
starch  is,  however,  greatly  superior  to  either  corn  starch  or  cassava 
starch  in  this  respect.  It  was  observed  that  the  viscosity  of  potato 
starch  is  reduced  by  agitation  more  easily  than  is  that  of  canna 
starch.  This  is  true,  especially  in  concentrations  of  about  2  per 
cent,  where  the  viscosity  begins  to  rise  abruptly  with  small  incre- 
ments of  starch. 

GELLING  STRENGTH 

Hot  starch  solutions,  which  were  prepared  like  those  used  in  the 
viscosity  tests,  were  pouied  into  test  tubes  one-half  inch  in  diameter 
and  allowed  to  cool  for  one  hour.  The  tubes  were  then  inverted. 
The  minimum  concentration  necessary  to  keep  the  mass  from  run- 
ning down  the  side  of  the  inverted  tube  was  termed  its  "gelling 
strength." 

The  gelling  strength  of  edible  canna  starch,  potato  starch,  corn 
starch,  and  cassava  starch  was  found  to  be  3.75,  3.25,  4,  and  6.25  per 
cent,  respectively.  Examinations  of  the  four  starches  at  the  concen- 
trations noted  above  showed,  however,  that  while  the  corn  starch 
and  the  cassava  starch  formed  a  definite  gel  structure,  which  re- 
tained its  shape  when  shaken  out  of  the  tube,  the  other  two  starches 
remained  as  nydrosols  or  possibly  as  plastic  gels  having  sufficiently 
high  viscosity  to  prevent  their  running  down  the  side  of  the  tube. 

USES 

Both  the  foliage  and  the  tubers  of  the  edible  canna  make  excellent 
feed  for  dairy  cows,  and  the  tubers  when  cooked  are  fairly  good  for 
pigs.  The  small,  immature  tubers  when  cooked  resemble  white  pota- 
toes in  taste  and  consistency,  but  soon  become  too  fibrous  to  be 
palatable.  The  tubers  are  little  used  for  human  consumption  in 
Hawaii. 

The  starch  would  seem  to  have  considerable  value  as  a  food  and 
for  industrial  uses.  A  very  pure  product  can  be  prepared  by  simply 
shredding  the  tubers,  mixing  the  pulp  with  water  and  passing  the 
whole  through  a  perforated  screen,  and  finally,  by  separating  the 
fecula  or  amylaceous  matter  from  the  fibrous  substance  by  sedimenta- 
tion. Owing  to  its  extraordinarily  large  granules,  the  starch  settles 
in  a  few  minutes  and  very  little  time  and  expense  is  required  to  free 


16  BULLETIN   54,    HAWAII   EXPERIMENT   STATION 

it  from  impurities.  The  starch  has  a  glossy  appearance,  with  a 
decided  glisten  in  certain  lights,  in  marked  contrast  with  the  smaller- 
grained  starches  which  are  of  dull  and  amorphous  appearance. 
When  cooked  it  forms  a  semi  translucent,  rather  sticky  mass,  such 
as  is  characteristic  of  potato  or  arrowroot  starch  but  different  from 
the  opaque  gel  obtained  from  corn  starch.  Since  pure  starches  are 
tasteless,  the  flavor  of  the  resultant  product  is,  of  course,  the  same 
regardless  of  the  kind  of  starch  used.  The  starch  is  often  recom- 
mended for  use  for  invalids  and  for  infants,  due  to  its  large  granules. 

SUMMARY 

Under  Hawaiian  conditions  edible  canna  can  be  grown  during  any 
season  of  the  year.  It  produces  its  maximum  yield,  however,  when 
grown  for  a  definite  period  at  an  altitude  of  less  than  1,500  feet. 

The  crop  is  adapted  to  either  long  or  short-rotation  periods,  and 
requires  a  loose,  loamy,  and  well-drained  soil  for  best  development. 
Cultivation  is  essential  when  the  crop  is  grown  in  a  hard,  compact 
soil. 

Edible  canna  is  free  from  attacks  of  injurious  insects  and  plant 
diseases,  and  produces  an  average  of  18  to  20  tons  of  tubers  per 
acre.  The  tubers  have  excellent  keeping  qualities.  Only  vigor- 
ous tubers  which  bear  unbruised  buds  should  be  selected  for  propa- 
gation. 

The  average  composition  of  a  hill  of  edible  canna  tubers  varies 
little  regardless  of  the  period  of  growth.  Weather  changes  stimulat- 
ing new  growth  may  cause  temporary  variation,  however. 

In  an  examination  of  immature,  mature,  and  old  tubers  from  a 
single  hill,  the  immature  tubers  were  found  to  differ  considerably 
from  the  mature  and  old  tubers,  which  were  similar  in  composition. 

Decided  changes  in  the  composition  of  the  tops  were  observed  to 
occur  in  the  transition  from  immaturity  to  maturity,  and  thence  to 
the  older  stages  of  growth.  The  nutritive  ratio  was  nearly  100  per 
cent  wider  for  the  old  than  for  the  immature  tops. 

Canna  grown  at  WTaimea,  Hawaii,  had  substantially  the  same 
composition  as  did  that  grown  at  the  central  station.  Tubers  which 
remained  in  the  ground  for  two  years  showed  a  loss  in  protein  con- 
tent but  otherwise  were  unchanged. 

The  feeding  value  of  both  the  tubers  and  the  tops  compares  favor- 
ably with  that  of  other  starch  and  forage  crops. 

Canna  starch  is  characterized  by  its  exceptionally  large  grains. 
Morphologically,  it  is  similar  to  potato  starch.  Its  viscosity  is 
greater  than  that  of  corn  starch  but  less  than  that  of. potato  starch. 

It  is  thought  that  edible  canna  starch  has  potential  possibilities 
both  as  an  edible  starch  and  for  commercial  uses.  It  makes  quick 
growth,  produces  heavy  yields,  and  can  be  harvested  at  any  age 
and  during  any  season,  and  should  therefore  lend  itself  admirably 
to  continuous  production  at  minimum  cost.  When  the  crop  is  grown 
on  a  large  scale,  the  tubers  should  be  produced  at  a  comparatively 
low  cost  per  ton.  The  starch  should  be  manufactured  at  excep- 
tionally small  cost  since  it  is  separated  with  ease.  Although  starch 
from  edible  canna  was  not  produced  in  Hawaii  for  industrial  purposes 
until  1922,  there  is  no  reason  why  it  should  not  become  as  popular 
as  potato  starch,  with  which  it  is  closely  comparable. 

o 


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